If I could make a weapon with existing materials.. I would make

The Chlorophyte Pike: has a 35% chance to inflict the Poisoned Debuff and shoots out a spore cloud like the Chlorophyte Saber does.

Crafted with:15 Chlorophyte Bars, 3 Jungle Spores and 1 Stinger

Crafted at: Mythril Anvil or Orichalcum Anvil it's a spear type weapon so.... yeah. Oh! and the spore cloud can also damage enemies through walls, basically a downgraded Mushroom Spear.